1. Field of the Invention
The present invention relates generally to communication networks.
2. Description of the Background Art
It is common in conventional computing environments to connect a plurality of computing systems or “hosts” through a communication medium often referred to as a network. The network permits the hosts to exchange and share information. Networks typically include various network devices, such as routers, switches, and hubs, in addition to the interconnected hosts.
Networks may be configured and graphically depicted in a wide variety of common topologies. The particular configurations of network communication links and devices between a particular pair of hosts wishing to exchange information may be widely varied. Any particular connection between two hosts attached to a network may be direct or may pass through a large number of intermediate devices in the network. Networks are therefore complex and vary in their configurations and topologies.
Certain network communication media and protocols are referred to as packet oriented. A protocol or communication medium may be said to be packet oriented in that information to be exchanged over the network is broken into discrete sized packets of information. A block of information to be transferred over the network is decomposed into one or more packets for purposes of transmission over the network. At the receiving end of the network transmission, the packets are re-assembled into the original block of data.
In general, each packet includes embedded control and addressing information that identifies the source device which originated the transmission of the packet and which identifies the destination device to which the packet is transmitted. Identification of source and destination devices is by means of an address associated with each device. An address is an identifier which is unique within the particular computing network to identify each device associated with the network. Such addresses may be unique to only a particular network environment (i.e., a network used to interconnect a single, self-contained computing environment) or may be generated and assigned to devices so as to be globally unique in co-operation with networking standards organizations. At one level of network communication, such addresses are often referred to as MAC (Media ACcess) addresses. Network protocols operable above this lowest level of communication may use other addresses, such as IP (Internet Protocol) addresses, for other purposes in the higher-level communication techniques.
Switches as conventionally practiced in the art often use a protocol commonly referred to as “spanning tree protocol” to discover the existence of redundant communication paths as known to a network of switches. There are three spanning tree protocols: IEEE 802.1d, 802.1w and 802.1s. See also the proposed IEEE standard P802.1p entitled “Standard for Local and Metropolitan Area Networks Supplement to Media Access Control (MAC) Bridges: Traffic Class Expediting and Dynamic Multicast Filtering.”